This proposal is directed at a careful analysis of possible familial distribution of lymphocytotoxic and anti-RNA antibodies among families of probands with Hodgkin's Disease as well as others with inflammatory bowel disease. In addition, lymphocyte subpopulation specificity of lymphocytotoxic antibodies will be examined, and an attempt made to determine whether such antibodies occurring in the sera of patients with systemic lupus erythematosus, Hodgkin's Disease, or inflammatory bowel disease show specificity for lymphocyte populations with increased suppressor T-cell activity. A study of mechanisms of inhibition of antibody mediated lymphocytotoxicity is planned. In addition, serial determinations of circulating immune complexes occurring during the course of pneumococcal infections will be performed.